Konrad Dabrowski Vadim V. Lozin Rajiv Raman Bernard Ries Colouring Vertices of Triangle-Free Graphs. 184-195 2010 WG http://dx.doi.org/10.1007/978-3-642-16926-7_18 conf/wg/2010 db/conf/wg/wg2010.html#DabrowskiLRR10